U.S. patent number 7,612,979 [Application Number 11/411,984] was granted by the patent office on 2009-11-03 for lightning protected aircraft telescopic refueling mast.
This patent grant is currently assigned to EADS Construcciones Aeronauticas, S.A.. Invention is credited to Fernando Cano Perez, Felipe Sequeiros Murciano.
United States Patent |
7,612,979 |
Sequeiros Murciano , et
al. |
November 3, 2009 |
Lightning protected aircraft telescopic refueling mast
Abstract
An aircraft telescopic in-flight refueling mast comprising a
metallic structural beam (31), electrically connected to the
aircraft by flexible conductive means (33), having inside a fixed
metallic tube (11) and a metallic telescopic tube (11) providing
the fuel conduit, and, attached to said beam (31), flight control
surfaces (41) and protection means against electric discharges,
specially lightning strikes and electro-static discharges,
including insulated means (39, 51) and low conductive means (15,
17) for reducing the lightning currents at a safe level and for
draining the static charge created during the refueling, and
conductive means (19, 21, 23, 33, 43) providing a safe lightning
current path and good electrical bonding for electro-static
discharge.
Inventors: |
Sequeiros Murciano; Felipe
(Madrid, ES), Cano Perez; Fernando (Madrid,
ES) |
Assignee: |
EADS Construcciones Aeronauticas,
S.A. (Madrid, ES)
|
Family
ID: |
36579385 |
Appl.
No.: |
11/411,984 |
Filed: |
April 26, 2006 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20070217116 A1 |
Sep 20, 2007 |
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Foreign Application Priority Data
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Mar 6, 2006 [EP] |
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06381009 |
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Current U.S.
Class: |
361/218; 361/212;
361/220 |
Current CPC
Class: |
B64D
45/02 (20130101); B64D 39/04 (20130101) |
Current International
Class: |
H05F
3/00 (20060101); H01H 3/00 (20060101); H01H
3/02 (20060101); H01H 47/00 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Paladini; Albert W
Assistant Examiner: Patel; Dharti
Attorney, Agent or Firm: Ladas and Parry LLP
Claims
The invention claimed is:
1. An aircraft telescopic in-flight refueling mast, comprising: a
metallic structural beam, electrically connected to the aircraft by
flexible conductive means, having inside a fixed metallic tube and
a metallic telescopic tube providing a fuel conduit, and, attached
to said beam, flight control surfaces; protection means against
electric discharges including lightning strikes and electro-static
discharges, said protection means including insulated means and low
conductive means for reducing the lightning currents to a safe
level and for draining static charge created during refueling, said
low conductive means including a concentric liner between the fixed
tube and the telescopic tube and a low conductive segment assembled
at the beginning of the telescopic tube constituting a dynamic seal
between both tubes, and conductive means providing a safe lightning
current path and good electrical bonding for electro-static
discharge.
2. An aircraft telescopic in-flight refueling mast comprising: a
metallic structural beam, electrically connected to the aircraft by
flexible conductive means, having inside a fixed metallic tube and
a metallic telescopic tube providing a fuel conduit, and, attached
to said beam, flight control surfaces protection means against
electric discharges including lightning strikes and electro-static
discharges, said protection means including insulating means which
include an insulated pipe section in the connection interface
between the fixed tube and the aircraft fuel system and insulated
fittings in those elements susceptible to inject current inside the
aircraft fuselage, low conductive means which include a concentric
liner between the fixed tube and the telescopic tube and a low
conductive segment assembled at the beginning of the telescopic
tube constituting a dynamic seal between both tubes, and conductive
means which include means providing electrical contact between the
fixed tube and the telescopic tube, sliding electrical contacts
between the flight control surfaces and the beam, and flexible
electrical connections between the structural beam and the
aircraft.
3. An aircraft telescopic in-flight refueling mast according to
claim 2, wherein said non conductive segment is assembled between a
first flange and a second flange connected by bolts.
4. An aircraft telescopic in-flight refueling mast according to
claim 2, wherein said means providing electrical contact between
the fixed tube and the telescopic tube comprise a sliding ring
connected to the telescopic tube through flexible conductors.
5. An aircraft telescopic in-flight refueling mast according to
claim 1, further comprising electro-static dischargers installed on
the outer extremities of metallic structural beam and aerodynamic
control surfaces.
Description
FIELD OF THE INVENTION
The invention relates to an aircraft telescopic in-flight refueling
mast protected against the effect of electric discharges, specially
lightning strikes and static discharge.
BACKGROUND
An in-flight aircraft may be subject to a direct strike of
lightning, which injects high current pulses into the airframe.
This event encompass both following categories of effects: Direct
attachment to the structure (local damage). Transfer lightning
current through the structure.
These effects shall not lead to a hazardous situation compromising
the continued safe flight and landing of the aircraft.
It is known that the aircraft protruding parts, areas called zone
1, are the most frequently struck by lightning. Rear locations of
those aircraft parts, areas called zone 1B, experience the most
severe ambient (2.times.10.sup.5 Amp, energy of 2.times.10.sup.6
Amp.sup.2 sec and charge transfer of 200 coulombs).
An Air-Air refueling operations consist in transferring fuel from a
tanker aircraft to a receptor one. The function is performed by a
conduit, which joins both aircrafts. Among others a telescopic
refueling mast may be used.
Aircraft refueling masts are usually located at the rear part of
the aircraft, therefore in the said lightning zone 1B.
Although refueling operation in stormy weather is not allowed, the
tanker aircraft may be struck in its way to the operational area.
For this purpose, at least, the telescopic refueling mast shall be
protected against lightning in its retracted position.
Due to the nature of the telescopic mast (capable to be extended
and retracted) the fuel conduct has sealing joints that will be
stressed by lightning currents, causing arcing and sparking with
energy (>200 uJ) enough to ignite fuel vapors.
One method of protection may be to electrically isolate the fuel
conduit, so no arcing is expected since no lightning currents area
allowed to flow inside. This means of lightning protection
conflicts with the requirement to drain the static charge build-up
caused by high-pressure fuel passage during refueling
operation.
Accumulation of static charges may cause a danger of ignition of
flammable vapors when uncontrolled discharges occur.
The present invention is intended to solve these drawbacks.
SUMMARY OF THE INVENTION
To accomplish this objective the present invention provides an
aircraft telescopic in-flight refueling mast comprising a metallic
structural beam, electrically connected to the aircraft by flexible
conductive means, having inside a fixed metallic tube and a
metallic telescopic tube providing the fuel conduit, and, attached
to said beam, flight control surfaces, also comprising protection
means against electric discharges, specially lightning strikes and
electro-static discharges, including insulated means and low
conductive means for reducing the lightning currents at a safe
level and for draining the static charge created during the
refueling, and conductive means providing a safe lightning current
path and good electrical bonding for electrostatic discharge.
With said protection means, the aircraft telescopic in-flight
refueling mast is adequately electrically bonded to the main
aircraft structure and can dissipate any charge accumulated in a
controlled manner to the atmosphere or ground.
The features, objects and advantages of the invention will become
apparent by reading this description in conjunction with the
accompanying drawings, in which:
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a partial sectional view of an aircraft telescopic
refueling mast according to this invention showing schematically
the assembly of the fixed and the telescopic tube.
FIG. 2 is a sectional view of an aircraft telescopic refueling mast
according to this invention showing schematically its electrical
connections to the aircraft.
FIG. 3 is a sectional detailed view showing schematically one
flight control surface attached to the structural beam of an
aircraft telescopic refueling mast according to this invention.
FIG. 4 is a top view of an aircraft telescopic refueling mast
according to this invention showing schematically its electrical
connections to the aircraft, flight control surface and
electro-static discharges location.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In order to explain the invention an example of the different
embodiments is described below showing the different features for
lightning protection and static charge conduction.
The design philosophy applied in this invention consists in
diverting, as much as possible, lightning currents away from
sealing joints or any part susceptible of producing
sparking/arcing, while keeping certain electrical conductivity
along the fuel-wet areas with two purposes: To equal electrical
potential of both tanker and refueled aircrafts, when they approach
one to the other. To drain the static charge created during the
refueling.
To accomplish these objectives, the present invention provides a
fix tube 11 and a telescopic tube 13 installed inside the metallic
structural beam 31 in such a way the only element susceptible to
receive a direct lightning strike, when the system is retracted, is
the external structural beam 31.
An electrical path to the aircraft fuselage is provided from the
worst-case lightning attachment to the mast flight control surfaces
(ailerons) 41 though the metallic structural beam 31, which is
connected back to the aircraft airframe by means of two flexible
electrical connections 33. A retainer device 37 (for example
arrestor hook) provides an additional electrical path between the
structural beam 31 and the aircraft when the mast is in the stowage
position.
The metallic fuel fix tube 11 is almost isolated from the metallic
telescopic tube 13 by a concentric liner 15 made of slightly
electrical conductive material, together with a segment 17 of the
telescopic tube 13 made of slightly conductive material as well
(for example carbon loaded plastic) assembled between flanges 61
and 63 connected by bolts 19, constituting a dynamic seal assembly.
Said concentric liner 15 prevents fretting between telescopic 13
and fix 11 tubes and is able to drain the static charge.
The electrical contact between the metallic fix tube 11 and the
metallic telescopic tube 13 is made through the metallic retainer
bolts 19 and a conductive ring 21 (for example graphite) outside
the fuel zone. The conductive ring 21 is connected to the
telescopic tube 13 by means of flexible conductors 23 and in
contact with the fix tube (face to face). Said retainer bolts 19
and conductive ring 21 allow therefore electrically jump said seal
assembly 17 as a safe current path (out of fuel area) from the
telescopic tube 13 to the fixed tube 11. This latest is
electrically bonded to the structural beam 31.
An insulated fuel feeding pipe section 39 before the connection to
the aircraft fuel system is provided to stop current to flow into
it. Likewise, an insulated covering 51 is provided at mast hoisting
point 35 to prevent current to flow trough the hoisting cable when
entering the aircraft fuselage, avoiding electromagnetic coupling
to system harnesses.
As it can be seen in FIG. 3, the way to electrically discharge the
mast aerodynamic control surface 41 to the metallic structural beam
31 is done by means of metallic sliding contacts 43, protecting the
mast control surfaces and avoiding damages to the bushing 45.
Electro-static dischargers 71 are installed on the outer
extremities of metallic structural beam 31 on the aerodynamic
control surfaces 41 to drain static charges to the atmosphere in a
safe way.
Although the present invention has been fully described in
connection with preferred embodiments, it is evident that
modifications may be introduced within the scope thereof, not
considering this as limited by these embodiments, but by the
contents of the following claims.
* * * * *